Good question, I used the term loosely, I guess its a matter of degree. Of the three examples I use, I guess Esperanto is the only genuinely "constructed" out of scratch, using ingredients from other languages. For Hebrew, a better term would be "revived". As far a "Macedonian" is concerned, the language pre-existed as a Bulgarian dialect for ages. In 1944 it was named "Macedonian" out of the blue by
Tito's government, and its grammar was codified so as to differente it from Bulgarian.
I agree that sign language is constructed. It is unfortunate that nobody thought of constructing an *international* SL. It is tragic that a user of American SL cannot communicate with a user of, say, Italian SL...